Catalytic hydrocarbon conversion and stripping process



De@ 6, 1966 H. P. WICKHAM ETAL 3,290,241

CATALYTIC HYDROCARBON CONVERSION AND STRIPPING PROCESS Filed Nov. 2s,1965 Begane/'afar /45 United States Patent O 3,290,241 CATALYTICHYDRCARBON CONVERSION AND STRHEPENG PRQCESS Henry P. Wickham, Glen Head,N.Y., and Louis F. Rice,

Barrancabermea, Colombia, assiguors to Pullman lincorporated, Chicago,Ill., a corporation of Delaware Filed Nov. 25, 1965, Ser. No. 509,864 9Claims. (Cl. 208-147) This application is a continuation-in-part ofapplication Serial No. 115,803, filed -June 8, 1961 now abandoned.

The present invention relates to the conversion of hydrocarbons. Morespecifically, the invention pertains to a method of convertingrelatively heavy or :high-boiling Hydrocarbons including topped orreduced crudes or similar heavy residue fractions to lower boiling rangefractions. Still more specifically, this invention is directed to amethod for cracking heavy gas oils and hydrocarbons boiling above`gas-oil boiling range in the presence of uidized solid catalyticmaterial to produce lower boiling range hydrocarbons and lhydrocarbonfeeds suitable for further cracking. y

In petroleum refining, crude petroleum .is first distilled to producedesired distillate fractions and a residue fraction. Motor fuels areproduced from the distillate fractions by a plurality of refiningtechniques known in the art, while the residue fraction is Iprocessed toobtain lubricating oils, waxes, asphalt, fuel oil, etc. However,difficulties have been experienced when attempting to crack *o residuefractions in the prior art processes because of the high ash content ofthe feed and the high rate of carbon formation which have led thoseskilled in the art to conclude that a crude residue is a highlyundesirable feed for a iluidized catalytic cracking process.

It is an object of this invention to provide an improved method andmeans for converting relatively high-boiling hydrocarbon feed materialsin the presence of fluidized catalytic material.

Another object of this invention is to provide an improved method forconverting residual oils including topped and reduced crudes in thepresence of uidized particle material.

Other objects and advantages of the present invention will lbecome moreapparent from the following description.

In catalytic racking operations, the conversion level described in termsof severity of operation may be attained by regulating the temperature,time of contact, catalyst to oil ratio and level of catalyst activity.It is the relative effect of these variables and the method ofcontrolling these variables with which the method and means of thisinvention is particularly concerned. Accordingly, the method of thisinvention is directed in-one aspect to maintaining relatively mildconversion conditions for the fresh feed material and substantially moresevere conversion conditions for residual components thereof.

The residual oil to be converted in accordance with this invention mayor may not contain gas oil components which can be satisfactorilyprocessed in separate cracking operations to primarily .gasoline boilingrange products. If the feed does contain such gas oil components, it ispreferred and an object of this invention to minimize conversion of suchgas oi-l components while maximizing conversion of any residualmaterials separated therefrom to a principal gas oil product. Theresidual oil to be processed in the method of this invention may be areduced crude constituting from about 20 percent to about 50 percent ofthe total crude and having an API *gravity in the range of from about 10to about 25 API. Gen- "ice erally, reduced crudes contain from about 30percent to about percent of the components boiling above 700 F., which,if properly handled, may be cracked to lower boiling range products andcoke.

In the method of this invention, any suitable siliceous crackingcatalyst may ybe employed for effecting the relatively mild and severecracking operations and the catalyst may be silica-alumina,silica-magnesia, silica-zirconia or mixtures thereof. l

These `and other objects are accomplished in accordance with the presentinvention for catalytically converting relatively high boiling productsto relatively -lower boiling products in a heat [balanced conversionsystem by maintaining a first relatively dense fluidized bed of catalystundergoing regeneration `by burning carbonaceous and hydrocarbonaceousmaterial contained on the surface of the catalyst in an atmospherecontaining oxygen. The regeneration zone is superimposed verticallyabove a relatively dense bed of catalyst participating in conversion ina reaction zone. Regenerated catalyst is flowed downwardly from theregeneration zone for discharge exclusively into the second dense bed atthe lower elevation. Freshly regenerated catalyst which is at a hightemperature relative to the catalyst undergoing conversion in the secondzone is mixed therewith in order to provide a catalyst mixture havingreduced activity and a temperature which is substantially lower thanthat of the freshly regenerated catalyst for initial contact withrelatively high boiling range hydrocarbon feed material in order toavoid overcracking of low boiling range components which may tbe presentin the feed. ^A confined upilowing suspension of such catalyst mixtureand oil is produced by contacting relatively high boiling range liquidhydrocarbon oil and solid material consisting of the aforementionedcatalyst mixture. The upflowing suspension is, preferably, contactedwith a relatively low boiling hydrocarbon liquid at a point above thebottom of the suspension. In another embodiment such catalyst mixture iscontacted with inert gaseous material, eg., steam. in order to produce aconfined upfiowing suspension which is contacted above the bottomthereof with liquid hydrocarbon feed material for conversion. Thecatalyst and oil suspension is discharged adjacent the upper level ofthe dense bed in the reaction zone and, preferably, above the level ofthe dense bed under conditions to separate vaporousv hydrocarbonmaterial from catalyst containing absorbed residual oil material whichis returned to the dense bed. The residual material isconverted to lowerboiling range products in the dense bed which affords extended contacttime for the residual material at an elevated temperature. The catalystmixture is stripped to remove volatile hydrocarbonaceous material andpassed upwardly into the regeneration zone.

The upfiowing confined suspension of catalyst and hydrocarbon materialproduced by contacting hydrocarbon liquid feed material and the catalystmixture contained in the second dense bed is maintained underhydrocarbon conversion conditions while maintaining a catalyst to oilratio in the suspension, preferably7 between about 25 and about 50:1and, most preferably, between about 35 and about 45 :1. Ashort contacttime is employed in the confined suspension, preferably, between about0.5 to about 2.5 seconds. Preferably, the catalyst mixture produced inthe dense bed in the reaction zone is maintained at a temperaturebetween about 925 F. and about 1075" F. The relatively high boilingrange liquid hydrocarbon oil, for example, which isintroduced as feed,and the catalyst mixture having a reduced activity, i.e., an activityintermediate between that of the freshly regenerated catalyst andcatalyst which has been in the reaction bed for an extended period oftime, are initially contacted ...a at the base of the upfiowing confinedsuspension within the above-stated temperature range.

In accordance with the method of the present invention, the catalystcirculation between the lower and the upper portion of the dense bed ofcatalyst in the reaction zone can be adjusted independently of thecatalyst circulation between the reaction zone and the regeneration zonein order to achieve the severity of conditions desired in both theconfined upowing suspension and the dense reaction bed. Preferably, thecatalyst circulation in the upiiowing confined suspension is maintainedabove about 3 times the catalyst circulation between the regenerationzone and the dense bed in the reaction zone.

The vaporous hydrocarbon material which is separated from catalyticmaterial above the dense bed in the reaction zone is passed to a productfractionat-or for separation into desired boiling range fractions.Preferably, the relatively high boiling liquid fraction separated in alower portion of the fractionation zone is recycled to the conversionzone and contacted with the catalyst mixture of reduced activity at thebase of the confined upowing suspension.

The removal and recovery of hydrocarbons from the catalyst is enhancedby positioning a stripping zone beneath and contiguous with the fluidbed of catalyst in the reaction zone so that hot freshly regeneratedcatalyst discharged into the dense fluid bed of catalyst is entrainedwith the catalyst entering the stripping section and stripping gasintroduced to the bottom portion thereof passed upwardly through thetotal iiuid bed of catalyst thereabove in the reaction zone.Accordingly, the continuous dense uid bed of catalyst in the reactionand stripping zones function in part as an enlarged high temperaturestripping zone wherein hydrocarbon constituents retained with thecatalyst are converted to lower boiling range products and recoveredfrom the catalyst. The stripped catalyst is thereafter removed from thebottom or lower portion of the stripping zone and passed to aregeneration zone for the removal of unstripped carbonaceous materialfrom the catalyst by burning in the presence of an oxygen-containinggas. During regeneration the catalyst is heated to an elevatedtemperature in the range of from about l050 F. to about l250 F., orhigher and sufficiently elevated for recycle to the fiuid bed ofcatalyst in the reaction zone to maintain the desired temperatureconversion conditions therein.

In the method of operation described with respect to this invention, theactivity of the freshly regenerated catalyst is reduced or modified byadmixture with the partially used catalyst of the process for treatingthe high boiling hydrocarbon feed material while simultaneouslyproviding the necessary endothermic heat to the fluid bed of catalyst inthe reaction and stripping zones wherein conversion and removal ofadsorbed hydrocarbons retained in the catalyst is effected at a highertemperature than that encountered by the feed material upon initialcontact with the catalyst. Accordingly, contact of hydrocarbon materialwith catalytic material under a relatively wide range of conversionconditions of time and temperature is permitted and the conditions ofseverity desired for conversion of different high boiling hydrocarbonsis readily obtainable in 4the method of this invention. A hydrocarbonfeed to be converted is introduced into the upiiowing confined stream ofcatalyst or riser-reactor within the reaction zone through a pluralityof separate and spaced apart nozzles or inlet points which are locatedat the bottom, intermediate and, preferably, in an upper portion of theriser, thereby permitting control of contact time with respect to theseparate hydrocarbon feeds and the catalyst. Where it is desired tointroduce hydrocarbon feed to the riser solely above the bottom thereof,relatively inert gasiform material, such as steam, is preferablyemployed as lift gas to form an upwardly flowing suspension of thecatalyst mixture. When converting heavy or high boiling hydrocarbons,such as reduced crudes, relatively inert gaseous material is preferablyernployed with the hydrocarbon feed to assist with atomization andpartial vaporization of the hydrocarbon feed for more suitabledistribution and intimate contact of the feed with the catalyst withinthe riser.

While the method of this invention is particularly directed -to theconversion of high boiling hydrocarbons such as topped and reducedcrudes or residual fractions, it is to be understood that lower boilingrange hydrocarbons, such as gas oils may also be converted to desiredproducts employing the method and means of this invention.

It is to be understood that a plurality of substantially verticallydisposed hydrocarbon riser-reactors can be employed within the dense bedof catalyst in the reaction zone for contact with a plurality ofhydrocarbon feed material. The riser-reactors are provided with variableorifice means at the bottom end thereof and a suitable discharge meansatthe upper end thereof which will change the direction of the verticallyflowing suspension outwardly and in a generally horizontal direction. Apreferred discharge means is a bird cage separator which is more fullydescribed with reference to the figure of the drawing.

Having thus given a general description of the improved method and meansof this invention, reference is now made to the drawings by way ofexample, which present a preferred embodiment of this invention.

Referring now tothe figure of the drawing, by way of example, a freshhydrocarbon liquid feed material of about 23.8 API gravity at atemperature of about 450 F. is introduced in conduit 14 which leads intobranched conduits 15 for introduction into riser conduit 16 confinedwithin a reactor-stripper zone 18. It is to be understood that one ormore risers 16 can be employed and the risers can be discharged above oradjacent the dense fiuid bed of catalyst interface depending upon theheight of catalyst bed maintained in the reaction zone. Riser 16extends, in a specific embodiment, substantially vertically upward froma lower portion of -a dense fiuid bed of catalyst 20 maintained in thelower portion of the reaction zone and discharges above the upper densebed level 22 of the fiuid bed of catalyst. Suitable dilute gasiformmaterial, such as dispersion steam, may be introduced by conduit 24 foradmixture with the fresh feed in conduit 14 passed to riser 16 viabranched conduits 15. A vertically movable hollow stem plug valve 26 isaligned with the bottom open end of riser 16 through which a recyclefeed material, more fully defined hereinafter, either with or Withoutdispersion steam, is passed by conduit 28 to valve 26. Conduit 30connected to conduit *28 is provided for introducing gasiform materialsuch as steam thereto. It is contemplated, in another embodiment of thisinvention, to introduce fresh feed to the bottom of riser 16 by valve 26and to introduce the recycle feed directly into the fiuid bed ofcatalyst in the reaction zone.

In this specific example, the fluid bed of catalyst 20 comprises amixture of freshly regenerated catalyst and catalyst of modifiedactivity having been circulated through zone 16. The catalyst mixture iscontrolled by withdrawal of catalyst from the bed and the addition ofhot freshly regenerated catalyst thereto to maintain a bed temperatureof at least about 950 F., in this example. Accordingly, the catalystwithdrawn from bed 20 and passed upwardly as a suspension in riser 16comprises a mixture -of used and freshly regenerated catalyst forinitial contact with the hydrocarbon feed material introduced thereto.The quantity of catalyst employed in riser 16 is sufficient to maintaina catalyst to oil ratio in the range of from about 25 to about 50,preferably from about 35 to about 45 to l, with the contact time withinthe riser 16 being in the range of from about 0.5 to about 2 seconds. Inthis specific example, a catalyst to oil ratio of about 43.5 to 1 isemployed in riser 16 and the riser discharge temperature is about 900 F.The suspension passeti upwardly through riser 16 is discharged into thedilute catalyst phase above the dense iiuid bed of catalyst 20 whereinvaporous hydrocarbon products are separated from the catalyst andwithdrawn from the reactor-stripper zone 18 for passage by conduit 32 tothe product fractionator (not shown).

The catalyst separated from the suspension discharged into the dilutephase of the reactor-stripper zone 18 together with any hydrocarbonmaterial absorbed on or entrained with this catalyst is returned to thedense bed of catalyst so that these hydrocarbons or hydrocarbonaceousmaterial are subjected to more severe conversion conditions withextended contact time and -a higher temperature of about 950 F.,substantially above the temperature employed in the riser.

As discussed hereinbefore, catalyst is continuously added to and removedfrom the dense bed of catalyst in the reaction zone with a portion ofthe withdrawn catalyst passing directly as a continuous downwardlymoving fluid bed of catalyst into a stripping zone .beneath the reactionzone. Stripping gas introduced to the bottom of the stripping zonethrough branched conduit 36 flows upwardly therethrough and through thefluid bed of catalyst in the reactor-stripper zone. products of reactionjoin with the hydrocarbon conversion products in the dilute phase andare passed to the product fractionator in conduit 32. The strippingsection is provided with a plurality of downwardly sloping disc shapedbaflle members 38. It is contemplated, however, to ernploy a pluralityof vertically extending transverse bathe members within the annularstripping section to provide a plurality of elongated stripping sectionsin place of the sloping baies shown.

The stripping section is fan annular section in view of riser conduit 40extending from the lower portion of the stripping section upwardlythrough the reactor and discharging in a regeneration zone positionedabove the reaction zone. In the speciiic arrangement shown, the strippedcatalyst enters the bottom open end of riser 40 wherein it is mixed witha gaseous material such as a portion of the oxygen-containing gasrequired to regenerate the catalyst introduced by hollow stem plug valve42 for flow upwardly through the riser as a suspension. The thus formedsuspension passes upwardly through riser It@ and is discharged .at atemperature of about 960 F., adjacent the upper or top portion of adense iiuid bed of catalyst 44 maintained in the lower portion ofregeneration zone 46. Air or a suitable oxygen-containing gas is passedto valve 42 by conduit 48 either with or without relatively inertgaseous material such as steam introduced by conduit 50. Generally, thequantity of oxygen employed in riser 40 is from 4about 5 to about 40percent of that required to regenerate the catalyst by Iburning ofcarbonaceous material deposited on the catalyst during the hydrocarbonconversion steps. The remaining portion -of air or oxygen containing gasrequired to regenerate the catalyst is supplied to the lower portion ofthe iiuid bed of catalyst in the regeneration zone, :as hereinafterdescribed. That is, a portion of the required regeneration air is passedby conduit 52 to air heater S4 connected to distributor manifold 56positioned in the lower portion of the regeneration zone. Conduit 58 isprovided for introducing fuel to heater 54 and conduit 66 connected toconduit 52 is provided for introducing emergency steam in the event ofloss of air to the system. The remaining portion of regeneration air ispassed by conduit 62 to heater 64 connected to distribtuor manifold 66.Conduit 68 is provided for introducing fuel to heater 64 and conduit 7-0connected to conduit 62 is provided for introducing emergency steam. Inthe regeneration zone, carbonaceous material remaining on the catalystis removed by burning under conditions to maintain a regeneration dilutephase temperature above the dense iuid bed of catalyst of about ll F.When oper-ating the apparatus so that riser 46 discharges into thedilute catalyst phase above the dense fluid bed of catalyst in theregen-y Stripping gas and stripped eration zone, the temperature of thedischarged suspension will be usually suliiciently low to have a coolingeffect on the dilute catalyst phase sufficient to minimize secondaryburning occurring in the cyclone separators positioned in theregenerator dilute phase.

Gaseous products of combustion pass from the regenerator dilute phasethrough a plurality of cyclone separators '74 and 76 for removal ofentrained catalyst therefrom before removal from the regeneration zoneby conduit 78. The gaseous products of combustion or hot flue gases maybe passed to a CO boiler or other suitable arrangement (not shown) forthe production of steam required in the process or they may be used todevelop power to drive a regeneration gas compressor by expansion intired turbines employed to generate process steam in a CO boiler orother suitable device. Conduit connected to distributor manifold 82 isprovided in the top portion of the regeneration zone for theintroduction of steam thereto.

Regenerated catalyst at a desired elevated temperature is withdrawn fromthe bed of catalyst in the regeneration Zone and passed to the lowerportion of the fluid bed of catalyst in th reaction Zone to maintain adesired tempera.- ture therein by standpipe 84' having a verticallymovable catalyst ow control plug valve 86 aligned with the bottom endthereof. Conduits 88 and 90 connected to standpipe 84 are provided forintroducing aeration gas to the upper and lower portions of thestandpipe and maintain the catalyst therein in a flowable condition.

The hydrocarbon conversion products containing entrained catalyst notcompletely removed by cyclone separator 92 are removed from the upperportion of the reaction zone and passed by conduit 32 to the productfractionator (not shown) for separation into desired fractions.

Having thus given a general description of the improved method and meansof this invention and set forth a specific example thereof, it isunderstood that no undue restrictions are to be imposed thereon byreason thereof, except as defined by the claims.

What is claimed is:

1. A method for catalytically converting relatively high boilinghydrocarbons to lower boiling products in a heat balanced conversionsystem which comprises: maintaining a first relatively dense fluidizedbed of catalyst undergoing regeneration in a regeneration zonesuperimposed vertically above a second relatively dense bed of catalystparticipating in conversion in a reaction zone, iiowing regeneratedcatalyst downwardly from said regeneration zone exclusively into thesecond dense bed to provide a catalyst mixture having reduced activityand a temperature which is substantially lower than that of the freshlyregenerated catalyst, contacting a relatively high boiling liquidhydrocarbon oil and solid material consisting of said catalyst mixtureto vaporize at least a portion of such liquid and to produce anupflowing confined suspension of catalyst and hydrocarbon material, andmaintaining hydrocarbon conversion conditions within the saidsuspension, discharging said suspension adjacent the upper level of saidsecond dense bed under conditions to separate vaporous material which iswithdrawn overhead and catalyst containing adsorbed residual oilmaterial which is returned directly to said dense bed, stripping saidcatalyst mixture and passing such stripped catalyst upwardly into saidregeneration zone.

2. A method for catalytically converting relatively high boilinghydrocarbons to lower boiling products in a heat balanced conversionsystem which comprises: maintaining a rst relatively dense fluidized bedof catalyst undergoing regeneration in a regeneration zone superimposedvertically above a second relatively dense bed of catalyst participatingin conversion in a reaction zone, flowing regenerated catalystdownwardly from said regeneration zone exclusively into the second densebed to provide a catalyst mixture having reduced activity and atemperature which is substantially lower than that of the freshlyregenerated catalyst, contacting a relatively high boiling liquidhydrocarbon oil and solid material consisting of said catalyst mixtureto vapon'ze at least a portion of such liquid and to produce an upowingconlined suspension of catalyst and hydrocarbon material, contactingsuch confined upllowing suspension above the bottom thereof with arelatively low boiling hydrocarbon liquid, and maintaining hydrocarbonconversion conditions within the said suspension, discharging saidsuspension adjacent the upper level of said second dense bed underconditions to separate vaporous material which is withdrawn overhead andcatalyst containing adsorbed residual oil material which is returneddirectly to said dense bed, stripping said catalyst mixture and passingsuch stripped catalyst upwardly into said regeneration zone.

3. A method for catalytically converting relatively high boilinghydrocarbons to lower boiling products in a heat balanced conversionsystem which comprises: maintaining a first relatively dense lluidizedbed of catalyst undergoing regeneration in a regeneration zonesuperimposed vertically above a second relatively dense bed of catalystparticipating in conversion in a reaction zone, owing regeneratedcatalyst downwardly from said regeneration zone exclusively into thesecond dense bed to provide a catalyst mixture having reduced activityand a temperature which is substantially lower than that of the freshlyregenerated catalyst, contacting a relatively high boiling liquidhydrocarbon oil and solid material consisting of said catalyst mixtureto vaporize at least a portion of such liquid and to produce an upowingconfined suspension of catalyst and hydrocarbon material, andmaintaining hydrocarbon conversion conditions within said suspensionwhile maintaining a catalyst to oil ratio between about and about 50:1,discharging said suspension adjacent the upper level of said seconddense bed under conditions to separate vaporous material which iswithdrawn overhead and catalyst containing adsorbed residual oilmaterial which is returned directly to said dense bed, stripping saidcatalyst mixture and passing such stripped catalyst upwardly into saidregeneration zone.

4. The method of claim 3 in which said catalyst to oil ratio is betweenabout and about 45:1.

5. The method of claim 3 in which the contact time in said confinedsuspension is between about 0.5 and about 2 seconds.

6. The method of claim 1 in which said vaporous material withdrawnoverhead is separated in a fractionating zone to obtain relatively lowboiling product and said relatively high boiling liquid fraction whichis employed in contacting said catalyst mixture.

7. A method for catalytically converting relatively high boilinghydrocarbons to lower boiling products in a heat balanced conversionsystem which comprises: maintaining a relatively dense -uidized bed ofcatalyst undergoing regeneration in the regeneration zone superimposedvertically above the second relatively dense bed of catalystparticipitating in conversion in a reaction zone, flowing regeneratedcatalyst downwardly from said regeneration Zone in a conned zonedischarging exclusively into the second dense bed and mixing suchregenerated catalyst and catalyst undergoing conversion to provide acatalyst mixture having desired temperature and activity for contactwith hydrocarbon feed material as hereinafter defined, contacting astream consisting of relatively high boiling hydrocarbon liquid andsolid material consisting of said catalyst mixture to vaporize at leasta portion of such liquid and to produce an upowing conned suspension ofcatalyst and hydrocarbon oil, contacting such coniined uptlowingsuspension and a relatively low boiling hydrocarbon liquid above thebottom thereof, and maintaining hydrocarbon conversion conditions withinthe said suspension including a catalyst to oil ratio between about 25and about 50:1, discharging said suspension adjacent the upper level ofsaid second dense bed under conditions to separate vaporous materialwhich is withdrawn overhead and catalyst containing adsorbed residualmaterial which is returned directly to said dense bed, introducingstripping gas into said second dense bed to strip the catalyst mixture,and passing stripped catalyst upwardly as a coniined stream within saidsecond dense bed into said regeneration zone.

8. The method of claim 7 in which catalyst is owed downwardly from saidsecond dense bed and passed through a baffled catalyst stripping zoneprior to passage of such catalyst upwardly into said regeneration zone.

9. The method for catalytically converting relatively high boilinghydrocarbons to lower boiling products in a heat balanced conversionsystem which comprises: maintaining a rst relatively dense fluidized bedof catalyst undergoing regeneration in a regeneration zone superimposedvertically above a second relatively dense bed of catalyst participatingin conversion in a reaction zone, tlowing regenerated catalystdownwardly from said regeneration zone exclusively into the second densebed to provide a catalyst mixture having reduced activity and atemperature which is substantially lower than that of the freshlyregenerated catalyst, contacting solid material consisting of saidcatalyst mixture with inert gaseous material to produce an upflowingconfined suspension of catalyst and inert material, contacting suchconned upiiowing suspension with relatively high boiling hydrocarbon,and maintaining hydrocarbon conversion conditions within said suspensionwhile maintaining a catalyst to oil ratio between about 25 and about50:1, discharging said suspension adjacent the upper level of saidsecond dense bed under conditions to separate vaporous material which iswithdrawn overhead and catalyst containing adsorbed residual oilmaterial which is returned directly to said dense bed, stripping saidcatalyst mixture and passing such stripped catalyst upwardly into saidregeneration zone.

References Cited by the Examiner UNITED STATES PATENTS 2,900,325 8/1959Rice et al. 208-147 DELBERT E. GANTZ, Primary Examiner.

H. LEVINE, Assistant Examiner.

1. A METHOD FOR CATALYTICALLY CONVERTING RELATIVELY HIGH BOILINGHYDROCARBONS TO LOWER BOILING PRODUCTS IN A HEAT BALANCED CONVERSIONSYSTEM WHICH COMPRISES: MAINTAINING A FIRST RELATIVELY DENSE FLUIDIZEDBED OF CATALYST UNDERGOING REGENERATION IN A REGENERATION ZONESUPERIMPOSED VERTICALLY ABOVE A SECOND RELATIVELY DENSE BED OF CATALYSTPARTICIPATING IN CONVERSION IN A REACTION ZONE, FLOWING REGENERATEDCATALYST DOWNWARDLY FROM SAID REGENERATION ZONE EXCLUSIVLEY INTO THESECOND DENSE BED TO PROVIDE A CATALYST MIXTURE HAVING REDUCED ACTIVITYAND A TEMPERATURE WHICH IS SUBSTANTIALLY LOWER THAN THAT OF THE FRESHLYREGENERATED CATALYST, CONTACTING A RELATIVELY HIGH BOILING LIQUIDHYDROCARBON OIL AND SOLID MATERIAL CONSISTING OF SAID CATALYST MIXTURETO VAPORIZE AT LEAST A PORTION OF SUCH LIQUID AND TO PRODUCE ANUPFLOWING CONFINED SUSPENSION OF CATALYST AND HYDROCARBON MATERIAL, ANDMAINTAINING HYDROCARBON CONVERSION CONDITIONS WITHIN THE SAIDSUSPENSION, DISCHARGING SAID SUSPENSION ADJACENT THE UPPER LEVEL